DE10000568C2 - Thermally insulated exhaust gas cleaning system - Google Patents

Description

The invention relates to a thermally insulated Exhaust gas cleaning system, as preferred in the exhaust system men of internal combustion engines is used.

Due to legal regulations, which are always higher here requirements for exhaust systems in automotive engineering exhaust systems have been ste in the past continuously developed. Of particular interest in this Context of reaching quickly, or maintaining suitable thermal conditions in the exhaust system, which is required for the best possible pollutant conversion become. One way of dealing with these thermal conditions to ensure consists in the thermal insulation of the Exhaust system compared to the environment.

In U.S. Patent 5,477,676 is a vacuum insulated catalytic converter described. The vacuum insulation can be according to the operating temperatures inside the catalytic converter can be adapted. That means, that at elevated temperatures the vacuum is caused by a gas is replaced to control heat dissipation from the Ab gas system and thus prevent overheating zubeugen. The vacuum insulated converter is additional surrounded by heat exchangers. In this U.S. patent still a jacket of the vacuum-insulated con described with a phase change material, wel ches is characterized in that it is in the area of Be operating temperatures of the catalytic converter the aggregate condition changes and in this way an increased degree can store thermal energy.

The devices described above isolate a ka talytic converter compared to a radially outer the environment. Because of an effective radial isolation heat conduction or heat radiation of the catalytic converter preferably in the axial direction the rest of the exhaust system.

The object of the present invention is an exhaust gas stem to indicate which an improved thermal Iso lation, in particular axial heat conduction or heat radiation from the catalytic converter from the rest of the exhaust system.

This object is achieved by the exhaust gas system of an internal combustion engine with the features of Claim 1 solved. Advantageous further education and training designs of the exhaust system are the subject of the depend claims.

The exhaust system according to the invention has an exhaust gas purification system system, which has an entry area, an exit area and has a central area. In the central area of the Exhaust system, a catalytic converter is arranged. The The exhaust gas cleaning system also has two honeycomb bodies on, with a first honeycomb body in the entry area and a second honeycomb body is located in the exit area. The two honeycomb bodies and the catalytic converter are carried out in this way and in the exhaust system arranges that these can be flowed through for an exhaust gas. The at the honeycomb body are characterized in that they are ther mix insulating against axial heat conduction or heat radiation from the catalytic converter into the other exhaust system act. Emission control systems according to the prior art often have a tube-like and discharge of the exhaust gas with funnel-shaped expansions for connection to an exhaust gas cleaning system. This are usually not thermally insulated from the environment exercise and therefore cool down faster. As a result the rapid cooling of the exhaust gas in these areas and the sufficient space, is preferred there Convection on. The thermally different conditions compared to the exhaust gas cleaning have the result that a uniform thermi level is sought. This is due to the Ausge staltung, the type of installation and / or the attachment of the Honeycomb body prevented according to the invention. The first Honeycomb body contrasts with thermal insulation upstream components of the exhaust system, the second honeycomb body opposite the following compo components.

According to one embodiment, the first and / or the second honeycomb body made of a thermal insulation material. If the honeycomb body and the catalytic cal converters touch one another indirectly or directly ren, due to thermally insulated material of the Wa body can be prevented from conduction. Consists no connection between a honeycomb body and the catalytic converter is an axial forwarding of the Heat in the honeycomb body which is dissipated on the honeycomb body radiated thermal energy from the converter as well hardly possible. It is particularly advantageous in this case context, the first and / or second honeycomb body ceramic material, but can be carried out advantageous measures according to the present ceramic honeycomb bodies difficult to achieve.

According to a further exemplary embodiment, the the first and / or the second honeycomb body is an electrical heater tongue on. This heater can be used for this purpose, for example a temperature gradient in the immediate vicinity compared to the temperature of the catalytic converter eliminate and thus the loss of its thermal energy counteract.

According to yet another embodiment, the first honeycomb body a first entrance face and a he first exit face, the first entry face is smaller than the first exit face. The first honeycomb body is arranged in the exhaust gas purification system in such a way that this with the first exit face to the catalytic converter is aligned. Such a conical shape guided honeycomb body has the advantage that this ver has relatively small entrance face, which current is directed upwards. In this way, the first wa body only a small area available, the given otherwise, heat to upstream components ten issues. Thus there is a withdrawal of thermal energy reduced from the emission control system.

Similarly, it is particularly advantageous to use the second Honeycomb body also conical and so in to position the exhaust gas cleaning system that its has a smaller second outlet surface downstream. On this way the heat emission will be increased if necessary downstream components of the exhaust system or avoided the environment.

According to a further exemplary embodiment, the Wa body and the catalytic converter spaced apart. Between a honeycomb body and there is an air gap in front of the catalytic converter handen. The air gap itself has relatively good thermal insulation properties if there is no convex in it tion trains. To do this, it must be particularly narrow and / or Have means for preventing convection. Beson it is therefore advantageous if the first and / or the second honeycomb body axial extensions in the air gap have inside. These axial extensions are of this type perform that convection in the air gap is reduced becomes. A reduced convection in the air gap prevents cooling of the catalytic converter at the front.

According to yet another embodiment the first and / or the second honeycomb body by winding  and / or stacked and at least partially structured foil layers. The first and / or the second Honeycomb bodies are characterized by the fact that the foils have a Have a film thickness of 0.015 to 0.035 mm. This very ge ring film thickness has the consequence that, viewed on the face side, the honeycomb body has an extremely low percentage of metal lischer filled area. The vast majority part is air, which insulates against axial heat conduction has an effect.

According to yet another embodiment, the first and / or the second honeycomb body with at least one egg ner thermally decoupled face. That be indicates that heat conduction also within a honeycomb body is hindered in the axial direction. A warm out replace a face that is usually cooler during the cooling process che with the inside of the honeycomb body can on this Way be reduced.

According to a further exemplary embodiment, the first and / or the second honeycomb body in their interior at least one slot. The slot is near an ther mix decoupled face arranged. The slot represents an air gap, which the heat conduction from the End face reduces to the inside. Particularly advantageous is to form the slot all the way around, this being itself spreads radially inwards from the outside. Particularly advantageous it is sticky if the slot has at least one notch. This means interruptions in the course of the slot, which the strength of the honeycomb body even under dynami guarantee shear stress.

According to yet another embodiment, a thermally decoupled end face achieved in that several slots, preferably in different levels, perpendicular to a preferred direction of flow of the Ab gases are arranged. The levels in which the slots are are arranged, are slightly spaced from each other. On in this way, the sheet-like insulation by means of minde least one slot in one plane on a predeterminable Volume area enlarged. This supports the thermal Decoupling the face. It is particularly advantageous at, several slots and notches in one level assign, the slots or notches in below different levels are staggered. So that is ge thinks that at least partially in the direction of flow Overlap of a first level slot and egg a notch of a subsequent level takes place. Such a Executed honeycomb body only offers a reduced axial heat conduction, because of this arrangement Art labyrinth for the heat flow is realized.

According to yet another embodiment the first and / or the second honeycomb body from the kataly table converter axially spaced only 1 to 2 mm. On this is a sufficiently large gap between the Honeycomb bodies and the converter available to a Heat conduction from the converter to the honeycomb bodies connect without forming a strong convection can. It is particularly advantageous if the honeycomb body to the catalytic converter by means of insulating Fasteners are spaced. Insulating fasteners elements prevent heat conduction and offer in addition, the possibility of a predeterminable distance between to ensure the honeycomb body and converter. The Stability and fatigue strength of the described exhaust gas series cleaning system can be increased.

According to a further embodiment, the Ab gas cleaning system with a catalytic converter executed, which thermally decoupled end faces has. Thus, additional and in the catalytic con verter integrated heat conduction blockages, which also act in the manner described above.

According to one, the catalytic converter is still wide Ren embodiment by winding and / or stacking generated, at least partially structured sheet metal layers. The Sheets are characterized by the fact that this is a sheet have a thickness of 0.08 mm to 0.11 mm. The usage thicker sheets in the catalytic converter in the opposite Set to the honeycomb bodies has the advantage that the catalytic cal converter can store more thermal energy and cools down much more slowly.

According to one, the exhaust gas cleaning system is still wide Ren embodiment with additional convection lock ren executed, which between the exhaust gas purification location and the catalytic converter, the first honeycomb body and the second honeycomb body are arranged. These convection barriers are particularly designed in this way leads to this, but without the current too strong hinder, radially into a gap in the outer area between one honeycomb body and the catalytic converter extend into it. Cooling down to the air gap end faces can be reduced.

The exhaust gas cleaning system is preferably designed in such a way that that it is thermally insulated radially outwards. The radial outside areas represent a considerable interface che to the environment, which is particularly important for the Mecha heat dissipation from the exhaust gas cleaning system is relevant to the environment. The thermal insulation in axial Direction, d. H. in the flow direction of the exhaust gas is esp especially required for exhaust systems that are also one of the have radial insulation.

According to a further embodiment, it is and / or second honeycomb body on the exhaust gas cleaning system thermally insulated. Especially with the Fi Fixation of conically shaped honeycomb bodies is a fastening This makes sense at the exhaust gas cleaning system. A thermally insulated connection also reduces heat pipe from the honeycomb body into the rest of the exhaust gas stem.

At least the first honeycomb body accordingly has an egg nem yet another embodiment, a catalytic effective surface on which the exhaust gas to be cleaned flows along and is implemented catalytically. In normal Operation of the exhaust system, i.e. at a temperature of ka talytic converter, which is effective for harmful is suitable, the ab is cleaned gases mainly through the converter. Still is one supporting catalytic activity of the honeycomb body partial and enables compliance with the required Ab gas regulations regarding the residual proportion of pollutants which are released into the environment.

A catalytically active upper is particularly advantageous area of the first honeycomb body with respect to the on jumping behavior of the exhaust system after a long break. After a long period of time the catalytic converter is out for example down to the external ambient temperature cooled. Needed after starting the engine the converter, precisely because of its otherwise desired large heat capacity, a certain period of time until this due to the exhaust gas flowing through it a temperature of e.g. B. has heated above 300 ° C to a enable effective pollutant conversion. To the front written cleaning effect of the exhaust system also in Ensuring this cold start phase is the first honeycomb body according to a further embodiment placed that he had a turnover rate in this phase Hydrocarbons and carbon monoxide of at least 80% after 10 to 20 sec. In particular, the wa body has a volume of 0.2 to 1.0 liters, preferably  of 0.6 liters.

The cold start behavior after a long break in operation can according to a further embodiment by a additional pre-catalyst can be improved, which the Exhaust system is upstream. This is closer to the Brenn arranged engine and is therefore hot through the exhaust gases. A catalytic implementation can succeed at this point after a shorter period The catalytic reaction also has an increase in Exhaust gas temperature, which then in the Exhaust system arranged downstream flows. Especially It is advantageous if the upstream converter elek is heatable. Is the necessary temperature in the Ab Once the gas system is reached, the downstream arrangement again bears nete catalytic converter for complete exhaust gas purification addition.

Further advantages and details of the invention Exhaust systems of an internal combustion engine are based on the preferred embodiment shown in the drawing Rungsbeispiele explained, but not to the invention is limited.

Show it:

Fig. 1 is a schematic representation of an execution example in full section of the exhaust gas purification system,

Fig. 2 is a side view of an embodiment of a honeycomb body,

Fig. 3 is a side view of another game Ausführungsbei a honeycomb body,

Fig. 4 is an end view of a game Ausführungsbei a honeycomb body and

Fig. 5 is an end view of a game Ausführungsbei a catalytic converter.

Fig. 1 shows an exhaust gas purification system 1 through which egg nem exhaust gas can flow in a preferred flow direction 21 . The exhaust gas purification system 1 has an entry area 2 , an exit area 3 and a central area 4 . A catalytic converter 5 is arranged in the central region 4 . A first honeycomb body 6 is located upstream in the inlet area 2 of the exhaust gas purification system 1 . In the exit area 3 , a second honeycomb body 7 is arranged. The honeycomb bodies 6 and 7 and the catalytic converter 5 can be flowed through for the exhaust gas. Furthermore, the exhaust gas purification system 1 under different means for thermal insulation, which are explained below.

The two honeycomb bodies 6 and 7 in Fig. 1 are designed conically. The first honeycomb body 6 has a small first entry end face 9 and a larger first exit end face 10 . The first honeycomb body 6 is oriented in such a way that the smaller first entry face 9 faces upstream. The heat dissipation from the first entry end face 9 to upstream areas of the exhaust gas cleaning system 1 can thus be reduced. The conical shape of the first wa benkörpers 6 has the result that it can be arranged relatively close to a pipe-like exhaust gas supply line. This is particularly advantageous since there is hardly any space for convection between the first honeycomb body 6 and the exhaust gas cleaning system 1 .

The second honeycomb body 7 is arranged essentially mirror-image to the first honeycomb body 6 . Accordingly, the second honeycomb body 7 has a second entry end face 11 , which is made larger than the second exit end face 12 . In this way, a reduced heat emission from the second exit end face 12 is ensured.

The exhaust gas purification system 1 of FIG. 1, each having a narrow air gap 14 between the first honeycomb body 6 and the catalytic converter 5 on the one hand, and the converter 5 and the second honeycomb body 7 running on the other. The spacing of the honeycomb bodies 6 and 7 from the catalytic converter 5 is ensured by means of thermally insulated fastening elements 22 . The narrow air gaps 14 and the thermally insulated fastening elements 22 prevent axial heat conduction from the catalytic converter 5 to the honeycomb bodies 6 and 7 .

In the case of air gaps 14 which are wide by design, the entire exhaust gas purification system 1 can also be designed on the outside with convection barriers 23 which, on the outside, hinder convection, but without greatly influencing the agbas flow.

In addition, the possibility of the arrangement 1 is shown schematically in Fig. Of a pre-catalyst 31 from the rest of the exhaust gas cleaning system 1 is illustrated, which is also a specific electrical heating 32 may include.

Fig. 2 shows a side view of an embodiment ei nes honeycomb body 6 or 7. In order to reduce convection in the adjacent air gaps 14 near the honeycomb body 6 or 7 , this honeycomb body has extensions 13 . The illustrated embodiment of the honeycomb body is made with partially structured film layers 15 , which were generated by winding and / or stacking. An individual foil layers 15 protrude beyond the end face of the wa benkörpers 6 or 7 . The axial extent 13 is consequently formed directly from the film layers 15 by larger-sized and / or displaced film layers relative to other layers.

Furthermore, the honeycomb body in FIG. 2 shows an electrical heating 8 , which is placed on the honeycomb body 6 or 7 . A heating wire 8 is shown as an example, which is wound around the honeycomb body 6 , 7 . The Folienla conditions of the honeycomb body 6 , 7 can also be used directly as elec trical heating resistors. An arrangement of a heating wire in the interior of the honeycomb body 6 , 7 is also possible. An electrically heatable honeycomb body 6 or 7 can be used both for short-term improvement of the cold start behavior after a long break in operation, and for maintaining a desired temperature in the exhaust gas cleaning system during long breaks in operation.

Fig. 3 shows a further embodiment of a honeycomb body 6 or 7 with thermally decoupled end faces 18th Thermally decoupled end faces 18 are ensured by slots 19 , which are preferably arranged in different planes 20 approximately perpendicular to the flow direction 21 . Fig. 3 shows that the slots 19 are 25 offset from each other. In this way, a kind of labyrinth is generated, which reduces the heat conduction from the inside of the honeycomb body 6 or 7 to the outside during the cooling process. The slots 19 are umlau fend formed and extend radially inwards. The dimensioning of the slots 19 is chosen so that the sta bility and strength of the honeycomb body 6 , 7 is still guaranteed ge.

Fig. 4 shows an end view of a honeycomb body 6 , 7 with film layers 15 , which were generated by winding and / or stacking. The sheet metal layers 15 are at least partially structured and are made with foils 16 , which have a predefinable foil thickness 17 . The honeycomb body by 6 , 7 of this embodiment has a catalytically active surface 29 .

Furthermore, an embodiment of the slots 19 is shown in FIG. 4. The slots 19 are spaced apart by notches 24 . The notches 24 contribute to the stability of the honeycomb body 6 , 7 .

Fig. 5 shows a section through a catalytic converter. The catalytic converter shown has at least partially structured sheet metal layers 26 which are produced by winding and / or stacking and which are made with sheets 27 of a predeterminable sheet thickness 28 . This catalytic converter cal 5 has thermally decoupled end faces 18 which are formed by a plurality of slots 19 and notches 24 .

LIST OF REFERENCE NUMBERS

1

emission control system

2

entry area

3

exit area

4

Central area

5

converter

6

first honeycomb body

7

second honeycomb body

8th

heater

9

first entrance face

10

first exit face

11

second entry face

12

second exit face

13

extension

14

air gap

15

film layer

16

foil

17

film thickness

18

thermally decoupled face

19

slot

20

level

21

flow direction

22

fastener

23

convection

24

score

25

offset

26

sheet metal layer

27

sheet

28

sheet thickness

29

surface

30

volume

31

precatalyzer

32

electric heating

Claims (26)

1. Exhaust system of an internal combustion engine, with an exhaust gas purification system ( 1 ), which has an entry area ( 2 ), an exit area ( 3 ) and a central area ( 4 ), with a catalytic converter ( 5 ) in the central area ( 4 ), and with a first honeycomb body by ( 6 ) in the inlet area ( 2 ) and a second honeycomb body ( 7 ) in the outlet area ( 3 ), the first ( 6 ) and the second ( 7 ) honeycomb body and the catalytic converter ( 5 ) for an exhaust gas can be flowed through, characterized in that the first ( 6 ) and / or the second honeycomb body ( 7 ) through its design, loading and / or arrangement means for thermal insulation ( 8 , 9 , 10 , 11 , 12 , 13 , 16 , 18 , 19 , 22 , 23 ) bil det, which reduce heat conduction and / or heat radiation from the catalytic converter ( 5 ) into the usual exhaust system. 2. Exhaust system according to claim 1, characterized in that the first ( 6 ) and / or the second honeycomb body ( 7 ) is made of thermally insulating material. 3. Exhaust system according to claim 2, characterized in that the first ( 6 ) and / or the second honeycomb body ( 7 ) are made of ceramic material. 4. Exhaust system according to one of claims 1 to 3, characterized in that the first ( 6 ) and / or the second honeycomb body ( 7 ) are electrically heated ( 8 ) leads out. 5. Exhaust system according to one of claims 1 to 4, wherein the first honeycomb body ( 6 ) has a first entry face ( 9 ) and a first exit face ( 10 ), characterized in that the first entry face ( 9 ) is smaller than the first exit face ( 10 ) and is aligned with the first exit end face ( 10 ) towards the catalytic converter ( 5 ). 6. Exhaust system according to one of claims 1 to 5, wherein the second honeycomb body ( 7 ) has a second entry face ( 11 ) and a second exit face ( 12 ), characterized in that the second entry face ( 11 ) is larger than the second exit is end face ( 12 ) and with the second entry face ( 11 ) towards the catalytic converter ( 5 ) is directed out. 7. Exhaust system according to one of claims 1 to 6, wherein between the first honeycomb body ( 6 ) and the catalytic converter ( 5 ) and between the two th honeycomb body ( 7 ) and the catalytic converter ( 5 ) each have a narrow air gap ( 14 ) is characterized in that the first ( 6 ) and / or the second honeycomb body ( 7 ) have axial extensions ( 13 ) into the air gap ( 14 ), which reduce a convection in the air gap ( 14 ). 8. Exhaust system according to one of claims 1 to 7, wherein the first ( 6 ) and / or the second honeycomb body ( 7 ) produced by winding and / or stacking, least least partially structured film layers ( 15 ), characterized in that the films ( 16 ) have a film thickness ( 17 ) of 0.015 to 0.035 mm. 9. Exhaust system according to one of claims 1 to 8, characterized in that the first ( 6 ) and / or the second honeycomb body ( 7 ) have at least one thermally decoupled end face ( 18 ). 10. Exhaust system according to claim 9, characterized in that the first ( 6 ) and / or the second honeycomb body ( 7 ) has at least one slot ( 19 ) in its interior, which is arranged near the at least one thermally decoupled end face ( 18 ) is. 11. Exhaust system according to claim 10, characterized in that the slot ( 19 ) is circumferential and extends radially inwards. 12. Exhaust system according to claim 10 or 11, characterized in that the slot ( 19 ) has at least one notch ( 24 ). 13. Exhaust system according to one of claims 10 to 12, characterized in that a plurality of slots ( 19 ), preferably in different planes ( 20 ), are arranged perpendicular to a preferred flow direction ( 21 ) of the exhaust gas. 14. Exhaust system according to claim 13, wherein the slots ( 19 ) each have at least one notch ( 24 ) ha ben, characterized in that the notches ( 24 ) are mutually offset ( 25 ) are arranged. 15. Exhaust system according to one of claims 1 to 14, characterized in that the first ( 6 ) and / or the second honeycomb body ( 7 ) from the catalytic converter ( 5 ) are axially spaced 1 to 2 mm. 16. Exhaust system according to one of claims 1 to 15, characterized in that the first ( 6 ) and / or the second honeycomb body ( 7 ) to the catalytic converter ter ( 5 ) by means of insulating fastening elements ( 22 ) are spaced. 17. Exhaust system according to one of claims 1 to 16, characterized in that the catalytic converter ( 5 ) has thermally decoupled end faces ( 18 ). 18. Exhaust system according to one of claims 1 to 17, wherein the catalytic converter ( 5 ) generated by winding and / or stacking, at least partially structured sheet metal layers ( 26 ), which are made with sheets ( 27 ) of a predetermined sheet thickness ( 28 ) , characterized in that the sheets ( 27 ) have a sheet thickness ( 28 ) of 0.08 mm to 0.11 mm. 19. Exhaust system according to one of claims 1 to 18, characterized in that the emission control system ( 1 ) has further convection barriers ( 23 ) which between the emission control system ( 1 ) and the catalytic converter ( 5 ), the first honeycomb body ( 6 ) and the second honeycomb body ( 7 ) are net angeord. 20. Exhaust system according to one of claims 1 to 19, characterized in that the emission control system ( 1 ) is thermally insulated radially outward. 21. Exhaust system according to claim 20, characterized in that the first ( 6 ) and / or the second honeycomb body ( 7 ) on the exhaust gas cleaning system ( 1 ) are thermally insulated. 22. Exhaust system according to one of claims 1 to 21, characterized in that the first ( 6 ) and / or second honeycomb body ( 7 ) have a catalytically active surface ( 29 ) along which the exhaust gas flows. 23. Exhaust system according to one of claims 1 to 22, wherein the first honeycomb body ( 6 ) has a catalytically active surface ( 29 ), characterized in that the first honeycomb body ( 6 ) is designed so that it very quickly in the cold start phase high turnover rate with respect to hydrocarbons and carbon monoxide, especially after 10 to 20 seconds at least 80%. 24. Exhaust system according to claim 23, characterized in that the first honeycomb body ( 6 ) has a volume of 0.2 to 1.0 liters, preferably of 0.6 liters. 25. Exhaust system according to one of claims 1 to 22, characterized in that the emission control system ( 1 ) is a pre-catalyst ( 31 ), in particular with a volume of 0.2 to 1 liter, preferably about 0.6 liters, upstream. 26. Exhaust system according to claim 25, characterized in that the pre-catalyst ( 31 ) is provided with an electrical heating's ( 32 ).